Yellow River superfine sand aggregate interface reinforcing agent as well as preparation and use methods thereof

Abstract

The invention relates to the technical field of building materials, in particular to a Yellow River superfine sand aggregate interface reinforcing agent and a preparation and use method thereof.The interface reinforcing agent is prepared from 0.05-0.1 part of graphene oxide powder, 50-100 parts of a silane coupling agent, 50-100 parts of nano-silicon dioxide, 10-30 parts of oxalic acid and 5000-7000 parts of water; graphene oxide powder, a silane coupling agent and nano silicon dioxide are jointly used for preparing an interface modifier for performing interface modification treatment on the Yellow River superfine sand, so that the interface bonding force between the Yellow River superfine sand and a cement hydration product is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to an interface enhancer for ultrafine sand aggregate from the Yellow River and a preparation and use method thereof. Background Art

[0002] There is a large amount of ultrafine sand formed by siltation in the middle and lower reaches of the Yellow River, which makes the middle and lower reaches of the Yellow River face serious riverbed uplift problems and urgently need to adopt certain measures to absorb it. The use of energy-saving and environmentally friendly new building materials to prepare concrete has a significant carbon emission benefit. Therefore, the use of ultrafine sand from the Yellow River to prepare concrete plays an important role in reducing carbon emissions and improving the image of the Yellow River Basin.

[0003] However, under the action of long-term water scouring, the surface of the particles of the Yellow River ultrafine sand is smoother than that of ordinary river sand and machine-made sand, which may lead to weak bonding with cement hydration products. Literature 1 (Du Xiaotong, Hu Kui, Zhang Taoli, et al. Research on interface enhancement method for preparing recycled concrete with Yellow River sand [J]. Municipal Technology, 2023, 41(08): 96-102.) Studies have shown that the performance of untreated Yellow River sand is often inferior to that of traditional aggregates. This is mainly because the interface between the surface of the Yellow River sand and the hydrated calcium silicate gel (CSH) is weakly connected, which has a certain negative effect on the compressive strength of concrete. This has become one of the main reasons restricting the promotion and utilization of the Yellow River ultrafine sand in concrete.

[0004] Regarding how to modify the aggregate, the Chinese invention with publication number CN 118684473A discloses a recycled concrete aggregate interface enhancer and its preparation method. This method uses cement, sodium silicate, calcium carbonate and silicon dioxide and other materials to mix in a certain proportion. The obtained interface enhancer can effectively improve the bonding performance between the interface of recycled concrete aggregate and the fresh slurry, and greatly improve the various performance indicators of concrete. However, the application target of this method is mainly for recycled aggregates to solve the problems of large porosity, high water absorption and low density of recycled aggregates. It may not be feasible to learn from this method for the Yellow River ultrafine sand, because the problems such as high water absorption of recycled aggregates are not reflected in the Yellow River ultrafine sand. Therefore, this similar method is not suitable for interface enhancement treatment of the Yellow River ultrafine sand.

[0005] In recent years, new carbon nanomaterials such as graphene oxide are increasingly used in cement concrete for interface modification. A Chinese invention with publication number CN114163258A discloses a method for enhancing the interface bonding force of concrete with graphene or graphene oxide and silica fume, which can enhance the compactness of the bonding interface by attracting hydrated calcium silicate gel to generate with the help of graphene materials, thereby improving the bonding strength of the concrete interface. However, the invention is applied to the modification treatment on the new and old concrete casting interface. Generally speaking, the surface composition of the concrete interface is complex and diverse, including cement hydration products, coarse and fine aggregates, and cement particles that are not fully hydrated. The above components are likely to be exposed, and the elements contained therein include but are not limited to elements such as Ca, Si, O, Mg, Al, and Fe. This is different from the surface of the simple Yellow River superfine sand. The Yellow River superfine sand is mainly composed of SiO2, and the composition is relatively simple. Therefore, if it is modified by the Yellow River superfine sand fine aggregate, it may not be suitable.

[0006] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art known to those skilled in the art. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a Yellow River ultrafine sand aggregate interface enhancer and a preparation and use method thereof, and an interface modifier is prepared by using graphene oxide powder, silane coupling agent and nano-silicon dioxide to perform interface modification on the Yellow River ultrafine sand, thereby enhancing its interface bonding strength with cement hydration products.

[0008] The first object of the present invention is to provide an interface enhancer for Yellow River ultrafine sand aggregate, which comprises, by weight:

[0009] 0.05-0.1 parts of graphene oxide powder, 50-100 parts of silane coupling agent, 50-100 parts of nano silicon dioxide, 10-30 parts of oxalic acid and 5000-7000 parts of water;

[0010] The principle of the present invention is as follows: the Yellow River ultra-fine sand is formed in a specific section of the Yellow River, where the water flow is extremely fast. The continuous scouring of the water flow makes the surface of the Yellow River ultra-fine sand relatively smooth. Compared with conventional river sand and machine-made sand, the surface lacks sufficient roughness, and the chemical bonding and mechanical intercalation between the sand and the CSH gel are weak, resulting in an insufficiently tight interface connection.

[0011] The amino group (-NH2) contained in the silane coupling agent is covalently bonded to the carboxyl group (-COOH) of graphene oxide through an amide bond (-CONH-) to form a "graphene oxide-silane coupling agent" complex. One end of the amide bond (-CONH-) can be connected to the ultrafine sand of the Yellow River, and the other end can be connected to the Ca in the CSH gel. 2+ Chelation can form stable Ca-CONH-R bonds, thus establishing strong interfacial bonding between the Yellow River ultrafine sand and cement paste;

[0012] The silane coupling agent is hydrolyzed to generate silanol groups (-Si-OH), and the hydroxyl groups (-OH) on the surface of nano-silica condense with the silanol groups (-Si-OH) to form a Si-O-Si network structure, constructing a three-dimensional cross-linking system of "graphene oxide-silane coupling agent-nano-SiO2" with the silane coupling agent as the main bridge, realizing the chemical bonding of the three. The terminal nano-SiO2 acts as a crystal nucleus in the cement hydration process, promoting the generation of hydration products around the interface of the Yellow River ultrafine sand, making the microstructure more compact, and further improving the mechanical properties and impermeability of the concrete;

[0013] Among them, graphene oxide is easy to agglomerate due to van der Waals forces at high concentrations. The introduction of a low proportion of 10-30 parts of oxalic acid can form a stable dispersion system to avoid desorption from aggregates due to physical adsorption. Oxalic acid, as a weak acid, can adjust the pH value of the reaction system and act as a dispersant to prevent nanoparticles from agglomerating.

[0014] As a preferred embodiment of the present invention, the silane coupling agent is an organic silane coupling agent;

[0015] More specifically, the organic silane coupling agent may be aminosilane, mercaptosilane, epoxysilane, vinylsilane or methacryloxysilane.

[0016] As a preferred embodiment of the present invention, the nano-silicon dioxide is hydrophilic nano-silicon dioxide;

[0017] The surface of hydrophilic nano-silica is rich in hydroxyl groups (-OH), which can react with Ca in cement hydration products (such as CSH gel). 2+ , Si-O- and other groups are combined through hydrogen bonds or chemical bonds to form a denser interface transition zone; the hydrophilic surface is more likely to attract water molecules and cement particles, accelerating the nucleation and growth of CSH gel on the surface of Yellow River sand, thereby reducing the interface porosity and improving the compressive strength of concrete; the formula of the present invention uses water as the main solvent, and the hydrophilic nano-silica can be evenly dispersed in water, avoiding the agglomeration problem caused by hydrophobicity and ensuring the uniformity of spraying or immersion treatment.

[0018] As a preferred embodiment of the present invention, the particle size of nano-silicon dioxide is 20-30nm. The particle size of 20-30nm can provide a larger crystal nucleus surface area, more effectively promote the generation of hydration products around the interface of the Yellow River ultrafine sand, make the concrete microstructure more compact, and thus improve the mechanical properties and impermeability of the concrete.

[0019] As a preferred embodiment of the present invention, the interface enhancer further comprises 1-3 parts of a defoaming agent by weight;

[0020] The formula of the interface enhancer contains surfactants such as silane coupling agents and nano-silicon dioxide, which are easy to introduce bubbles during mixing. If the bubbles remain on the surface of the Yellow River sand or in the modifier coating, microporous defects will be formed, weakening the mechanical bite effect between the aggregate and the cement paste. The defoamer reduces the surface tension of the system, destroys the stability of the bubbles, and reduces the formation of pores.

[0021] The dosage of 1-3 parts can not only meet the defoaming needs, but also avoid the side effects caused by excessive dosage.

[0022] As a preferred embodiment of the present invention, the defoamer is a polyether-modified silicone defoamer;

[0023] In the polyether-modified silicone molecule, the siloxane segment (hydrophobic) and the polyether segment (hydrophilic) form an amphiphilic structure, which enables it to penetrate into the interface area of ​​the Yellow River ultrafine sand-cement paste and be compatible with the aqueous system, solving the foam problem of the multiphase system during concrete mixing; the polyether-modified silicone defoamer has no chemical conflict with the silane coupling agent, nano-silica and other components in the formula, avoiding system stratification or failure of traditional defoamers due to polarity differences; after defoaming, the dynamic adsorption of the polyether segment inhibits the generation of new foam, ensuring the stability of the interface modifier during storage and construction.

[0024] The second object of the present invention is to provide a method for preparing an interface enhancer of Yellow River ultrafine sand aggregate, comprising the following steps:

[0025] S1: adding graphene oxide powder into water and dispersing by ultrasonic to form graphene oxide dispersion;

[0026] Specifically, deionized water is used to avoid the introduction of calcium, magnesium and other ions, which may prevent side reactions with oxalic acid or silanol groups (such as the formation of calcium oxalate precipitation) and affect the stability of the interface enhancer.

[0027] The ultrasonic dispersion time is 30 minutes, so that the graphene oxide powder is evenly dispersed in the deionized water to form a graphene oxide dispersion. The purpose of this step is that graphene oxide is easy to form agglomerates due to its huge specific surface area and strong van der Waals force. Ultrasonic dispersion uses the high-frequency vibration and cavitation effect of ultrasound to effectively break up these agglomerates and disperse them into single nanoparticles or small agglomerates, thereby improving its dispersion stability.

[0028] S2: dissolving the silane coupling agent in water, adding oxalic acid to adjust the pH, then adding the graphene oxide dispersion, heating and stirring to form a composite solution;

[0029] More specifically, the silane coupling agent and deionized water are mixed at a mass ratio of 1:40, heated in a water bath at a water bath temperature of 60° C., stirred by magnetic stirring for 2 hours;

[0030] Silane hydrolysis is an endothermic reaction. Heating the temperature to 60°C can significantly increase the hydrolysis rate. Oxalic acid remains stable at 60°C, avoiding pH loss caused by high-temperature decomposition. Magnetic stirring and continuous shear force destroy the van der Waals aggregation of graphene oxide, fully exposing its surface and increasing the contact area with the silane coupling agent.

[0031] In this step, the silane coupling agent is hydrolyzed to generate a silanol group (-Si-OH), and at the same time, the amino group (-NH2) is covalently bonded to the carboxyl group (-COOH) of graphene oxide through an amide bond (-CONH-) to form a "graphene oxide-silane coupling agent" complex, which has both the reinforcing properties of graphene oxide and the interfacial bonding ability of silane; the reaction equation is as follows:

[0032] -COOH + -NH2 → -CONH- + H2O;

[0033] S3: adding nano-silicon dioxide into the composite solution, heating and stirring to obtain a mixed solution;

[0034] Specifically, the heating method adopts water bath heating, the water bath temperature is 50°C, the heating can increase the molecular movement rate and accelerate the reaction, the stirring time is 1 hour, the condensation reaction of the silane coupling agent and the nano-silicon dioxide requires about 30-60 minutes to reach equilibrium, and the 1 hour stirring can cover the entire reaction process to ensure the formation of a stable Si-O-Si bond in the interface enhancer;

[0035] In this step, the hydroxyl groups (-OH) on the surface of nano-silica condense with the silanol groups (-Si-OH) generated by the hydrolysis of the silane coupling agent to form a Si-O-Si network structure, thereby constructing a three-dimensional cross-linked system of "graphene oxide-silane coupling agent-nano-SiO2" with the silane coupling agent as the main bridge, thereby achieving chemical bonding among the three.

[0036] S4 defoams the mixed solution and adjusts the pH to 4-5 with oxalic acid to obtain an interface enhancer;

[0037] Specifically, shear stirring is performed simultaneously during the defoaming process, and the shear stirring parameter is stirring at 300 rpm for 20 min;

[0038] The mixed liquid contains surface active ingredients such as silane coupling agent and nano-silicon dioxide, which are prone to generate bubbles during shearing and stirring. Defoaming treatment can reduce the surface tension of the system, destroy the stability of bubbles, and avoid residual bubbles that lead to coating defects or decreased interfacial bonding strength.

[0039] More specifically, the defoaming treatment method is to add a defoaming agent to the mixed solution, and the defoaming agent needs to be evenly dispersed under high-speed shearing to avoid excessive local concentration leading to particle agglomeration;

[0040] Silane coupling agent hydrolyzes fastest under weak acid conditions. Oxalic acid releases H + Adjust the pH to the ideal range to ensure that the ethoxy groups are fully converted into silanol groups; oxalic acid can complex the free metal ions in the system to prevent them from competitively binding with silanol groups or amino groups, thereby avoiding a decrease in interfacial binding strength; the carboxyl groups contained in oxalic acid hydrogen bond with the hydroxyl groups on the surface of the nanoparticles, further inhibiting agglomeration and maintaining the long-term stability of the dispersion.

[0041] As a preferred embodiment of the present invention, after adding oxalic acid in step S2, the pH is adjusted to 3.0-4.5;

[0042] Among them, oxalic acid is a weak acid, which is used to catalyze the hydrolysis reaction of silane coupling agent (generating silanol groups), and pH 3.0-4.5 is the best acidic condition for silane hydrolysis.

[0043] As a preferred embodiment of the present invention, the concentration of the graphene oxide dispersion is 0.01-0.10 g / L;

[0044] When the concentration of graphene oxide dispersion exceeds 0.01g / L, it is easy to agglomerate due to van der Waals forces to form hundreds of nanoscale aggregates, reducing the interface bonding efficiency. By limiting the upper limit of the concentration to 0.1g / L and combining oxalic acid as a dispersant, nanoscale monodispersity can be achieved.

[0045] The third object of the present invention is to provide a method for using the Yellow River ultrafine sand aggregate interface enhancer, wherein the washed and dried Yellow River ultrafine sand is immersed in the prepared interface enhancer, and then taken out and dried;

[0046] Water washing can remove dust, clay and organic impurities attached to the surface of the Yellow River ultrafine sand, preventing pollutants from hindering the chemical bonding between the interface enhancer and the sand particles;

[0047] During the soaking process, the nano-silica and silane coupling agent in the interface enhancer fully penetrate into the micropores and surface of the sand particles through soaking to form a "graphene oxide-silane coupling agent-nano-SiO2" composite coating layer. At the same time, the amino group of the silane coupling agent reacts with the carboxyl group of graphene oxide to form an amide bond, and the silanol group of the silane condenses with the hydroxyl group on the surface of the sand particles to achieve double chemical anchoring; the drying process promotes the volatilization of water and ethanol (silane hydrolysis byproduct), accelerates the condensation of silane to form a dense siloxane network, and enhances stability;

[0048] The immersion method is simple to operate, compatible with existing concrete aggregate pretreatment production lines, and can process Yellow River sand in batches at a controllable cost.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The synergistic effect of graphene oxide and silane coupling agent in the interface modifier significantly enhances the interfacial bonding force between the Yellow River ultrafine sand and cement paste. One end of the amide bond (-CONH-) carried by the "graphene oxide-silane coupling agent" complex can be connected to the Yellow River ultrafine sand, and the other end can be connected to the Ca in the CSH gel. 2+ Chelation forms a stable Ca-CONH-R bond, thereby establishing a strong interfacial bonding force between the Yellow River ultrafine sand and cement paste. This bonding force is stronger than that of graphene oxide alone combined with hydration products;

[0051] (2) In addition, in the "graphene oxide-silane coupling agent-nano-SiO2" structure, the nano-SiO2 at the end acts as a crystal nucleus during the cement hydration process, promoting the generation of hydration products around the interface of the Yellow River ultrafine sand, making the microstructure more compact, and further improving the mechanical properties and impermeability of the concrete. Through this interface modification treatment, the application performance of the Yellow River ultrafine sand in concrete has been significantly improved, providing the possibility for its wide application in the field of building materials;

[0052] (3) The use of the interface modifier in the present invention enables the Yellow River ultrafine sand to be effectively utilized, reducing the cost of building materials. In addition, the nano-silica and silane coupling agent in the interface modifier further optimize the surface properties of the Yellow River ultrafine sand, making it more evenly dispersed in concrete, thereby improving the overall performance of the concrete. This interface modification treatment method is simple, low-cost, and easy to industrialize. It has broad application prospects and promotion value, and provides strong support for the sustainable development of the Yellow River Basin. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The present invention is a schematic flow diagram of a method for preparing an interface enhancer for ultrafine sand aggregate from the Yellow River. DETAILED DESCRIPTION

[0054] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0055] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from the description, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0056] Secondly, the term "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0057] Sources of raw materials used in the specific implementation method:

[0058] Table 1

[0059] Components Commercial sources Graphene oxide powder Jiaxing Bona New Materials Co., Ltd. Silane coupling agent Dongguan Kangjin New Material Technology Co., Ltd. oxalic acid Nanchang Xinchao Chemical Co., Ltd. Nano Silica Shanghai Zhenlishi Network Technology Co., Ltd. Deionized water Jingjiang Hengxin Environmental Protection Equipment Co., Ltd.

[0060] Embodiment 1:

[0061] A Yellow River ultrafine sand aggregate interface enhancer, comprising:

[0062] Graphene oxide powder, silane coupling agent, nano silicon dioxide, oxalic acid and water, wherein the silane coupling agent is gamma-aminopropyltriethoxysilane.

[0063] Reference Figure 1 The method for preparing the above-mentioned Yellow River ultrafine sand aggregate interface enhancer comprises the following steps:

[0064] S1: 50 mg of graphene oxide powder was added to 5000 mL of deionized water and ultrasonically dispersed for 30 min to form a graphene oxide dispersion;

[0065] S2: Dissolve 50 g of γ-aminopropyltriethoxysilane in 2000 mL of deionized water, set a water bath at 60 °C with magnetic stirring for 3 hours, add 20 g of oxalic acid to adjust the pH to 3.0-4.5 at the beginning of stirring, stir for 1 hour, add the graphene oxide dispersion prepared in S1, and continue stirring for 2 hours to form a composite solution;

[0066] S3: adding 60 g of nano-silicon dioxide into the composite solution, stirring for 1 h in a water bath at 60° C. to obtain a mixed solution;

[0067] S4 After the mixed solution is cooled to room temperature, 2 g BYK-024 defoamer is added and stirred at a low speed for 30 min. During the process, oxalic acid is added dropwise until the pH value of the solution is adjusted to 4-5 to obtain an interface enhancer.

[0068] Embodiment 2:

[0069] S1: 55 mg of graphene oxide powder was added to 5000 mL of deionized water and ultrasonically dispersed for 30 min to form a graphene oxide dispersion;

[0070] S2: 60 g of γ-aminopropyltriethoxysilane was dissolved in 2000 mL of deionized water, and magnetic stirring was performed at 60 °C in a water bath for 3 hours. 20 g of oxalic acid was added dropwise at the beginning of stirring, and after stirring for 1 hour, the graphene oxide dispersion prepared in S1 was added, and stirring was continued for 2 hours to form a composite solution.

[0071] S3: adding 60 g of nano-silicon dioxide into the composite solution, stirring for 1 h in a water bath at 60° C. to obtain a mixed solution;

[0072] S4 After the mixed solution is cooled to room temperature, 2 g BYK-024 defoamer is added and stirred at a low speed for 30 min. During the process, oxalic acid is added dropwise until the pH value of the solution is adjusted to 4-5 to obtain an interface enhancer.

[0073] Embodiment 3:

[0074] S1: 60 mg of graphene oxide powder was added to 5000 mL of deionized water and ultrasonically dispersed for 30 min to form a graphene oxide dispersion;

[0075] S2 dissolved 60 g of γ-aminopropyltriethoxysilane in 2000 mL of deionized water, set a water bath at 60° C. with magnetic stirring for 3 hours, added 20 g of oxalic acid dropwise at the beginning of stirring, stirred for 1 hour, added the graphene oxide dispersion prepared in S1, and continued stirring for 2 hours to form a composite solution.

[0076] S3: adding 70 g of nano-silicon dioxide into the composite solution, stirring for 1 h in a water bath at 60° C. to obtain a mixed solution;

[0077] S4 After the mixed solution is cooled to room temperature, 2 g BYK-024 defoamer is added and stirred at a low speed for 30 min. During the process, oxalic acid is added dropwise until the pH value of the solution is adjusted to 4-5 to obtain an interface enhancer.

[0078] Embodiment 4:

[0079] S1: 70 mg of graphene oxide powder was added to 5000 mL of deionized water and ultrasonically dispersed for 30 min to form a graphene oxide dispersion;

[0080] S2: 60 g of γ-aminopropyltriethoxysilane was dissolved in 2000 mL of deionized water, and magnetic stirring was performed at 60 °C in a water bath for 3 hours. 20 g of oxalic acid was added dropwise at the beginning of stirring, and after stirring for 1 hour, the graphene oxide dispersion prepared in S1 was added, and stirring was continued for 2 hours to form a composite solution.

[0081] S3: adding 70 g of nano-silicon dioxide into the composite solution, stirring for 1 h in a water bath at 60° C. to obtain a mixed solution;

[0082] S4 After the mixed solution is cooled to room temperature, 2 g BYK-024 defoamer is added and stirred at a low speed for 30 min. During the process, oxalic acid is added dropwise until the pH value of the solution is adjusted to 4-5 to obtain an interface enhancer.

[0083] The ultrafine sand of the Yellow River is soaked in the interface enhancer prepared in the above Examples 1 to 4 at room temperature for 24 hours, and then taken out and naturally air-dried for concrete preparation;

[0084] Comparative Example 1:

[0085] No treatment is done on the ultrafine sand from the Yellow River;

[0086] Comparative Example 2:

[0087] The graphene oxide dispersion prepared in step S1 of Example 1 was used to soak the ultrafine sand from the Yellow River for 24 hours, and then taken out and naturally air-dried for concrete preparation;

[0088] Comparative Example 3:

[0089] The composite solution prepared by S1 and S2 in Example 1 was used to soak the Yellow River ultrafine sand for 24 hours, and then taken out and naturally air-dried for concrete preparation;

[0090] Comparative Example 4:

[0091] The mixed solution prepared in steps S1-S3 of Example 1 was used to soak the Yellow River ultrafine sand for 24 hours, and then taken out and naturally air-dried for concrete preparation.

[0092] Performance Test:

[0093] The ultrafine sand from the Yellow River prepared by the above method is used to prepare C30 concrete, and the concrete mix ratio is: cement: 230kg / m 3 , fly ash: 80kg / m 3 , mineral powder 70kg / m 3 , machine-made sand 600kg / m 3 , Yellow River ultrafine sand 200kg / m 3 , 5~20mm crushed stone 1100kg / m 3 , water 170kg / m 3 .

[0094] Put cement, fly ash, mineral powder, machine-made sand and processed Yellow River ultrafine sand into a mixer in proportion and stir at a low speed for 1 to 2 minutes to make all solid materials preliminarily mixed and uniform; on the basis of dry mixing, gradually add water and admixtures; increase the stirring speed and continue stirring for 3 to 5 minutes to make the concrete mixture reach a uniform state; pour the concrete mixture into a mold and vibrate it on a vibration table for 10 seconds to eliminate bubbles in the concrete and ensure its compactness; cover the surface of the poured concrete with plastic film and move it into a standard curing room (20±2℃, humidity ≥95%) for curing for 3d, 7d and 28d, and then test its compressive strength.

[0095] Compressive strength: Referring to GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete", the C30 concrete of Examples 1-4 and Comparative Examples 1-4 was tested for 3d, 7d and 28d day compressive strength, and the results are recorded in Table 2.

[0096] Table 2

[0097]

[0098] From the data in Table 2, it can be seen that after the interface enhancer of the present invention is used to treat the ultrafine sand of the Yellow River, the compressive strength of the prepared C30 concrete is significantly improved. In Examples 1-4, the 3d compressive strength of the concrete treated with the interface enhancer is between 17.8-18.3MPa, the 7d compressive strength is between 28.1-30.1MPa, and the 28d compressive strength is between 41.2-43.2MPa; while in the untreated comparative example 1, the 3d compressive strength is only 12.9MPa, 7d is 17.2MPa, and 28d is 28.6MPa. Pa; Comparative Examples 2-4 respectively used part of the products in the preparation process of the interface enhancer to treat the Yellow River ultrafine sand, and their strength improvement effects were not as good as those of the complete interface enhancer. This is because the silane coupling agent in the interface enhancer was hydrolyzed to generate silanol groups, and at the same time, the amino group (-NH2) and the carboxyl group (-COOH) of the graphene oxide were covalently bonded through an amide bond (-CONH-) to form a "graphene oxide-silane coupling agent" complex. One end of the amide bond (-CONH-) can be connected to the Yellow River ultrafine sand, and the other end can be connected to the Ca in the CSH gel. 2+ Chelation forms a stable Ca-CONH-R bond; in addition, nano-silica forms a "graphene oxide-silane coupling agent-nano-SiO2" structure with graphene oxide and silane coupling agent, and the nano-silica at the end acts as a crystal nucleus in the cement hydration process, promoting the formation of hydration products around the interface of the Yellow River ultrafine sand, making the microstructure more compact; in Comparative Example 4, since no defoaming treatment was performed and oxalic acid was not added to adjust the pH of the solution, the number of bubbles in the solution increased, and graphene oxide was prone to agglomeration, so that the interface enhancer did not achieve the desired effect.

[0099] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A Yellow River ultrafine sand aggregate interface enhancer, characterized in that: By weight, the interface enhancer includes: 0.05-0.1 parts of graphene oxide powder, 50-100 parts of silane coupling agent, 50-100 parts of nano silicon dioxide, 10-30 parts of oxalic acid and 5000-7000 parts of water.

2. The Yellow River ultrafine sand aggregate interface enhancer according to claim 1, characterized in that: The silane coupling agent is an organic silane coupling agent.

3. The Yellow River ultrafine sand aggregate interface enhancer according to claim 1, characterized in that: The nano silicon dioxide is hydrophilic nano silicon dioxide.

4. The Yellow River ultrafine sand aggregate interface enhancer as claimed in claim 3, characterized in that: The particle size of the nano silicon dioxide is 20-30 nm.

5. The Yellow River ultrafine sand aggregate interface enhancer according to claim 1, characterized in that: The interface enhancer also includes 1-3 parts of a defoaming agent by weight.

6. The Yellow River ultrafine sand aggregate interface enhancer as claimed in claim 5, characterized in that: The defoamer is a polyether-modified organic silicon defoamer.

7. The method for preparing the Yellow River ultrafine sand aggregate interface enhancer according to any one of claims 1 to 6, characterized in that: The steps include: S1: adding the graphene oxide powder into the water and dispersing by ultrasonic to form a graphene oxide dispersion; S2: dissolving the silane coupling agent in the water, adding the oxalic acid to adjust the pH, then adding the graphene oxide dispersion, heating and stirring to form a composite solution; S3 adding the nano silicon dioxide into the composite solution, heating and stirring to obtain a mixed solution; S4: defoaming the mixed solution, adjusting the pH to 4-5 with oxalic acid, and obtaining the interface enhancer.

8. The method for preparing the Yellow River ultrafine sand aggregate interface enhancer according to claim 7, characterized in that: After adding the oxalic acid in step S2, the pH is adjusted to 3.0-4.

5.

9. The method for preparing the Yellow River ultrafine sand aggregate interface enhancer according to claim 7, characterized in that: The concentration of the graphene oxide dispersion is 0.01-0.10 g / L.

10. A method for using the Yellow River ultrafine sand aggregate interface enhancer as claimed in any one of claims 1 to 6, characterized in that: The washed and dried Yellow River ultrafine sand is immersed in the prepared interface enhancer, and then taken out and dried.

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